Assigning mobile users in a half-frequency division duplex (hfdd) system to uplink (ul) sub-frames and to downlink (dl) sub-frames

ABSTRACT

Methods assigning mobile users in a half-frequency division duplex (HFDD) system to first and second UL groups of an uplink (UL) sub-frame, and to first and second UL groups of a downlink (DL) sub-frame, where the UL sub-frame has a first carrier frequency and the DL sub-frame has a second carrier frequency, are disclosed. One method includes determining a type of data, a receive CINR (carrier interference plus noise ratio), and a Doppler frequency parameter, for a plurality of mobile users. The mobile users to are assigned to the first UL group, second UL group, first DL group and second DL group based on time durations of the first UL group, second UL group, first DL group and second DL group, and at least one parameter of the determined parameters of the mobile users.

FIELD OF THE DESCRIBED EMBODIMENTS

The invention relates generally to wireless communications. More particularly, the invention relates to assigning mobile users in a half-frequency division duplex (HFDD) system to uplink (UL) sub-frames and to downlink (DL) sub-frames.

BACKGROUND

Frequency Division Duplex (FDD) and Time Division Duplex (TDD) are two prevalent duplexing schemes used in wireless networks. FDD, which historically has been used in voice-only applications, supports two-way radio communication by using two distinct radio channels. Alternatively, TDD uses a single frequency to transmit signals in both the downstream and upstream directions.

For FDD systems, one frequency channel is transmitted downstream from a radio A to radio B. A second frequency is used in the upstream direction and supports transmission from radio B to radio A. Because of the pairing of frequencies, simultaneous transmission in both directions is possible. To mitigate self-interference between upstream and downstream transmissions, a minimum amount of frequency separation can be maintained between the frequency pair.

For TDD systems, a single carrier frequency channel is used to transmit signals in both the downstream and upstream directions.

Half Frequency Division Duplex (HFDD) provides a duplexing scheme in which a downstream user receives signals on one carrier frequency over a first period of time, and transmits signals on another carrier frequency over a second period of time.

It is desirable to have a TDD system implementation that is operable as an HFDD system.

SUMMARY

An embodiment includes a method of assigning mobile users in a half-frequency division duplex (HFDD) system to a first UL group and second UL group of an uplink (UL) sub-frame, and to a first DL group and a second DL group of a downlink (DL) sub-frame. This embodiment further includes the UL sub-frame being assigned a first carrier frequency and the DL sub-frame being assigned a second carrier frequency. The method includes determining a type of data, determining a receive CINR (carrier interference plus noise ratio) of the mobile user, and determining a Doppler frequency parameter, for each mobile user of a plurality of mobile users. The plurality of mobile users to are assigned to the first UL group, the second UL group, the first DL group and the second DL group based on time durations of the first UL group, the second UL group, the first DL group and the second DL group, and based on and at least one of the data type, CINR, Doppler frequency spread of the mobile user, and a number of mobile users previously assigned to the first UL group, the second UL group, the first DL group and the second DL group.

Other aspects and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an example of a cellular network.

FIG. 2 shows an example of frames of frequency division duplex transmission signals.

FIG. 3 shows an example of frames of half frequency division duplex (HFDD) transmission signals.

FIG. 4 is a flow chart that includes steps of a method of assigning mobile users to a first group or a second group of downlink and uplink HFDD frames.

FIG. 5 is a flow chart that includes steps of a method of assigning mobile users in a half-frequency division duplex (HFDD) system to a first UL group and second UL group of an uplink (UL) sub-frame, and to a first DL group and a second DL group of a downlink (DL) sub-frame.

DETAILED DESCRIPTION

Methods and apparatuses for assigning mobile users in a half-frequency division duplex (HFDD) system to uplink (UL) sub-frames and to downlink (DL) sub-frames are disclosed. Embodiments of the methods generally include assigning each of the mobile users to groups based on a type of data, a receive CINR (carrier interference plus noise ratio), and/or a Doppler frequency parameter of the mobile user. The different groups include downlink (DL) and uplink (UL) sub-frames that are of different time durations.

FIG. 1 shows an example of a cellular network. This exemplary network includes base stations 110, 120 wirelessly communicating with mobile users 130, 132, 134, 140, 142. The cellular network can be, for example, an FDD (or HFDD) network in which downstream traffic from a base station to a mobile user can be allocated to one frequency channel, and upstream traffic from the mobile user to the base station can be allocated to another frequency channel. However, as will be described, sub-frames of the UL channel and the DL channel of different allocated groups can include different time durations. The time durations of the UL and DL of the different groups can influence how the mobile users are assigned to the different groups for UL and DL communication.

As shown, the mobile users can be fixed (such as, users 130, 134, 140, 142) or the users can be in motion (such as, user 132). As will be described, the mobile user in motion has a different Doppler parameter (such as, maximum Doppler frequency or Doppler frequency spread) than a mobile user that is fixed. The Doppler parameter of the mobile user can influence the assignment of the mobile user to the one of the different groups.

The users can be located at an edge of a cell (such as user 134) or the users can be located proximate to a base station. The proximity (as well as other factors) of the mobile user to the base station, influences the CINR of signals transmitted between the base station and the mobile user. The CINR of the mobile user can influence the assignment of the mobile user to the one of the different groups.

Additionally, the type of data being utilized by the mobile user can vary. For example, the data type of the mobile user can be voice (VoIP), web-centric data or video. Depending upon the data type, and characteristics of the data (for example, primarily upstream or primarily downstream traffic), the mobile user is assigned a group accordingly.

FIG. 2 shows an example of frames of frequency division duplex transmission signals. As shown, a downlink sub-frame 218 is dedicated to downlink communications, and an uplink sub-frame 228 is dedicated to uplink communications. The downlink frame 218 occupies a different frequency channel than the uplink frame 228 as indicated by the frequency axis of FIG. 2.

As shown, the downlink frame 210 includes a preamble 212, a MAP 216, an FCH (frame control header) 214, and a data region 218. The MAP 216 operates as a pointer to the data region that defines its location, size and MCS (modulation and coding scheme).

As shown, the uplink frame 220 includes a control region 222 and a data region 228. The control region 222 provides information transmitted by the mobile user, such as, for example, ACK/NACK (Acknowledgement/Negative Acknowledgement) of downlink transmissions, CQICH (channel quality information channel, for example, CINR), and ranging that is used for timing adjustments.

FIG. 3 shows an example of frames of half frequency division duplex (HFDD) transmission signals. The frames of the HFDD signals include characteristics of both FDD and TDD signals. A first group (Group 1) includes the downlink (DL1) sub-frame and the uplink (UL1) sub-frame. The second group (Group 2) includes the downlink (DL2) sub-frame and the uplink (UL2) sub-frame. As will be described, a useful feature of the sub-frames as shown and described is that the time duration of the uplink and downlink sub-frames of each group have different time durations. This feature is advantageously used for assigning different mobile users associated with a base station to the groups (Group1, Group2).

As shown, the downlink frame (that includes the DL1 sub-frame and the DL2 sub-frame) additionally includes a preamble 312, FCH and a MAP 314. These features can additionally be considered when assigning mobile users to the groups.

As can be observed, the embodiment of the UL and DL frames of FIG. 3 include DL1 sub-frame and the UL1 sub-frame of the first group are orthogonal in time. Additionally, the DL2 sub-frame and the UL2 sub-frame of the second group are orthogonal in time.

It can also be observed that the time durations of DL1 sub-frame and the UL1 sub-frame of the first group are different, and the time durations of the DL2 sub-frame, and the UL2 sub-frame of the second group are different. However, the time duration of the downlink frame that includes the DL1 sub-frame and the DL2 sub-frame is approximately the same as the time duration of the uplink frame that includes the UL1 sub-frame and the UL2 sub-frame.

FIG. 4 is a flow chart that includes steps of a method of assigning mobile users to a first group or a second group of downlink and uplink HFDD frames. A first step 410 includes making Doppler and CINR measurements of signals received by a mobile user. A second step 420 includes comparing the CINR measurement with a function of the Doppler measurement (f(Doppler)) and comparing a difference with a predetermined threshold C. If the difference is less than the threshold C, then the mobile user is assigned to the second group—the group that is located the farthest away from the preamble, if the difference is greater than the threshold C, then the measurements of the mobile user are additionally processed. The f(Doppler) is a correction term (fudge factor) to augment the CINR measurement.

A third step 430 includes determining a loading factor of the base station. If the loading factor is less than a threshold L, then the mobile user is assigned to the second group. If the loading factor is greater than the threshold L, then the mobile user is assigned to the first group. The loading factor defines the number of active mobile users connected to a particular base station that have data for transmission.

FIG. 5 is a flow chart that includes steps of a method of assigning mobile users in a half-frequency division duplex (HFDD) system to a first UL group and second UL group of an uplink (UL) sub-frame, and to a first DL group and a second DL group of a downlink (DL) sub-frame. For this embodiment, the UL sub-frame being is assigned a first carrier frequency and the DL sub-frame is assigned a second carrier frequency, the method comprising. A first step 510 includes for each mobile user of a plurality of mobile users, determining a type of data. A second step 520 includes for each mobile user, determining a receive CINR (carrier interference plus noise ratio) of the mobile user. A third step 530 includes for each mobile user, determining a Doppler frequency parameter. A fourth step 540 includes assigning the plurality of mobile users to the first UL group, the second UL group, the first DL group and the second DL group based on time durations of the first UL group, the second UL group, the first DL group and the second DL group, and based on and at least one of the data type, CINR, Doppler frequency spread of the mobile user, and a number of mobile users previously assigned to the first UL group, the second UL group, the first DL group and the second DL group.

The Doppler frequency parameter provides an indication of movement of a mobile user with respect to a base station. Doppler frequency parameters that can be measured include, for example, a maximum Doppler frequency and a Doppler frequency spread.

The maximum Doppler frequency indicates a speed of the mobile user or a rate of changes in the received signal across multiple OFDM symbols. The Doppler frequency spread indicates the rate of change in the received signal across a single OFDM symbol period. The Doppler frequency and/or the Doppler frequency spread can be determined by the mobile user using the received downlink preambles transmitted from the base station. The Doppler frequency and/or the Doppler frequency spread can be determined by the base station using received uplink pilot tones transmitted from the mobile unit.

An embodiment includes the time duration of the first UL group of the UL sub-frame being different than the time duration of the first DL group of a corresponding DL sub-frame. This embodiment also includes the time duration of the second UL group of the UL sub-frame being different than the time duration of the second DL group of a corresponding DL sub-frame.

An embodiment includes multiple mobile users being assigned to either a first group or a second group, wherein the first group includes the first UL group and the first DL group, and the second group includes the second UL group and the second DL group. As described, the assignments are based on measurements of communication signals at the mobile users.

An embodiment includes mobile users having a downlink CINR below a downlink threshold being assigned to a one of the first group and the second group corresponding to a longer time duration of the first DL group and the second DL group.

Another embodiment includes mobile users having an uplink CINR below an uplink threshold are assigned to a one of the first group and the second group corresponding to a longer time duration of the first UL group and the second UL group.

An embodiment includes the mobile users having a greater downlink information bit rate requirement than an uplink information bit rate requirement are assigned to a one of the first group and the second group corresponding to a longer time duration of the first DL group and the second DL group. The longer duration DL allows for greater down link information bit rates. As described, the DL and UL of each group are asymmetric. Generally, the downlink information bit requirement of each mobile user is dependent upon an application of the mobile user, and therefore, the application being used by the mobile user can be used to influence the group assignment of each mobile user.

For an embodiment, the mobile users determined to be communicating through voice over Internet protocol (VoIP) on an uplink are assigned to a one of the first group and the second group corresponding to a longer time duration of the first UL group and the second UL group.

For an embodiment, the mobile users determines to be communicating through voice over interne protocol (VoIP) on an uplink below a threshold, are assigned to a one of the first group and the second group corresponding to a longer time duration of the first DL group and the second DL group. That is, for example, while a mobile user is operating a voice connection, the group assignment of the mobile user can adjust or adapt to the mobile user transmitting voice data through the uplink (talking), and then the group assignments can adjust or adapt to when the mobile user is receiving voice data through the downlink (listening).

An embodiment includes a first symbol of the DL sub-frame including a preamble. As previously described, the preamble is a set of known tones. This embodiment can further include assigning mobile users having a Doppler measured above a threshold being assigned to a one of the first group and the second group that includes a preamble.

An embodiment includes the base stations per performing the mobile user assignments. Embodiments include the base station informing the mobile users of the group assignments. Embodiments can also include the mobile users assisting the base station.

Each mobile user carries over state information when switching between the first group and the second group. A non-exhaustive list of examples of the state information includes a connection ID, ARQ state, and HARQ state. The state information can be carried over between groups by, for example, the base station informing the mobile user of the state information.

Although specific embodiments have been described and illustrated, the described embodiments are not to be limited to the specific forms or arrangements of parts so described and illustrated. The described embodiments are limited only by the appended claims. 

1. A method of assigning a mobile user to one of a first uplink portion and a second uplink portion of an uplink sub-frame, and to one of a first downlink portion and a second downlink portion of a downlink sub-frame, the method comprising: determining a receive CINR (carrier to interference-plus-noise ratio) of the mobile user; and assigning the mobile user to one of the first uplink portion and the second uplink portion of the uplink sub-frame, and to one of the first downlink portion and the second downlink portion of the downlink sub-frame based on the receive CINR.
 2. The method of claim 1, further comprising determining a number of mobile users currently assigned to each of the first uplink portion, the second uplink portion, the first downlink portion and the second downlink portion, wherein the assigning of the mobile user to one of the first uplink portion and the second uplink portion of the uplink sub-frame, and to one of the first downlink portion and the second downlink portion of the downlink sub-frame is based on the receive CINR and the number of mobile users currently assigned to each of the portions.
 3. The method of claim 1, farther comprising determining a Doppler frequency parameter associated with the mobile user, wherein the assigning of the mobile user to one of the first uplink portion and the second uplink portion of the uplink sub-frame, and to one of the first downlink portion and the second downlink portion of the downlink sub-frame is based on the receive CINR and the Doppler frequency parameter.
 4. The method of claim 3, further comprising determining a difference between the receive CINR and a function of the Doppler frequency parameter; and comparing the difference to a predetermined threshold, wherein the downlink sub-frame includes a preamble portion, and wherein, if the difference is less than the predetermined threshold, the mobile user is assigned to the one of the first downlink portion and the second downlink portion that is located furthest from the preamble portion within the downlink sub-frame.
 5. The method of claim 1, further comprising comparing the receive CINR to a predetermined threshold, wherein the first downlink portion has a different duration than the second downlink portion, and the first uplink portion has a different duration than the second uplink portion.
 6. The method of claim 5, wherein if the receive CINR is below the predetermined threshold, the mobile user is assigned to the one of the first downlink portion and the second downlink portion that is longer in duration.
 7. The method of claim 5, wherein if the receive CINR is below the predetermined threshold, the mobile user is assigned to the one of the first uplink portion and the second uplink portion that is longer is duration.
 8. A method of assigning a mobile user to one of a first communication group and a second communication group, the first communication group including a first downlink portion of a downlink sub-frame and a first uplink portion of an uplink sub-frame, the second communication group including a second downlink portion of the downlink sub-frame and a second uplink portion of the uplink sub-frame, the method comprising: determining a receive CINR (carrier to interference-plus-noise ratio) of the mobile user; determining whether the mobile user is communicating using voice over internet protocol (VoIP); and assigning the mobile user to one of the first communication group and the second communication group based on at least one of the receive CINR and whether the mobile user is using VoIP.
 9. The method of claim 8, wherein the first downlink portion has a different duration than the second downlink portion, and the first uplink portion has a different duration than the second uplink portion.
 10. The method of claim 9, further comprising determining whether the mobile user is one of talking or listening using the voice over internet protocol.
 11. The method of claim 10, wherein the determining of whether the mobile user is one of talking or listening is performed by comparing an uplink usage of the mobile user to a predetermined threshold.
 12. The method of claim 11, wherein if the uplink usage of the mobile user is above the predetermined threshold, the mobile user is assigned to the communication group that includes the one of the first uplink portion or the second uplink portion that has the longer duration.
 13. The method of claim 11, wherein if the uplink usage of the mobile user is below the predetermined threshold, the mobile user is assigned to the communication group that includes the one of the first downlink portion or the second downlink portion that has the longer duration.
 14. A wireless communication device capable of assigning a mobile user to one of a first communication group and a second communication group, the first communication group including a first downlink portion of a downlink sub-frame and a first uplink portion of an uplink sub-frame, the second communication group including a second downlink portion of the downlink sub-frame and a second uplink portion of the uplink sub-frame, the wireless communication device comprising: one or more processor configured to: determine a receive CINR (carrier to interference-plus-noise ratio) of the mobile user; and assign the mobile user to one of the first communication group and the second communication group based on at least one of the receive CINR and another parameter.
 15. The wireless communication device of claim 14, wherein the first downlink portion has a different duration than the second downlink portion, and the first uplink portion has a different duration than the second uplink portion.
 16. The wireless communication device of claim 15, wherein the one or more processor is further configured to compare an uplink bit rate of the mobile user to a downlink bit rate of the mobile user.
 17. The wireless communication device of claim 16, wherein if the uplink bit rate exceeds the downlink bit rate, the one or more processor is configured to assign the mobile user to the communication group that includes the one of the first uplink portion or the second uplink portion that has the longer duration.
 18. The wireless communication device of claim 16, wherein if the uplink bit rate is below the downlink bit rate, the one or more processor is configured to assign the mobile user to the communication group that includes the one of the first downlink portion or the second downlink portion that has the longer duration.
 19. The wireless communication device of claim 15, wherein the one or more processor is further configured to compare the receive CINR to a predetermined threshold, and wherein if the receive CINR is below the predetermined threshold, the mobile user is assigned to the communication groups that includes the one of the first downlink portion and the second downlink portion that is longer in duration.
 20. The wireless communication device of claim 15, wherein the one or more processor is further configured to compare the receive CINR to a predetermined threshold, and wherein if the receive CINR is below the predetermined threshold, the mobile user is assigned to the communication group that includes the one of the first uplink portion and the second uplink portion that is longer is duration. 